microsoft exchange

In Outlook for Mac, first open the Outlook menu and clear Work Offline if it is selected; then test the same mailbox in your organization’s Outlook on the web site to distinguish a password problem from an Outlook configuration or server-discovery problem.^1^

1. Test the account outside Outlook for Mac

Connect the Mac to the network normally used for Exchange—such as the corporate network or required VPN—and sign in to Outlook on the web.

• Web sign-in fails: The password, account status, or username format needs correction by the Exchange/Active Directory administrator.
• Web sign-in succeeds: The credentials work for webmail. Outlook may still require a different username format or authentication method, or Autodiscover may be failing.

2. Check and re-enter the Outlook account settings

1. In Outlook, select Tools → Accounts.
2. Select the Exchange account.
3. Verify the email address, username, and Exchange server information supplied by the administrator.
4. If setup is incomplete, remove the failed account and add it again through Outlook → Settings → Accounts → + Add Account.
5. Enter the mailbox email address and follow the prompts.^2^

Do not substitute Microsoft 365 server names for an on-premises mailbox. Obtain the organization’s Exchange server name from its administrator; existing settings can be viewed under the account’s Advanced → Server tab when that option is available.^3^

3. Match Outlook’s authentication method to the environment

The correct choice is version- and deployment-dependent:

• Current Outlook for Mac on-premises mailbox support: The mailbox must be on Exchange Server 2016 or later, and the documented authentication methods are NTLM or Basic. Outlook must also be licensed through an eligible volume or Microsoft 365 business/enterprise license and downloaded from the Microsoft 365 portal rather than the Apple App Store.^4^
• Outlook 2016 for Mac in an organization configured for Kerberos: While connected to the corporate network, select Kerberos from the account’s Method menu, then select an existing Kerberos ID or Create a new Kerberos ID. For NTLM, Basic, or other supported methods, select User Name and Password instead.^5^

Check the installed Outlook version under Outlook → About Outlook, then have the Exchange administrator confirm which branch applies.

4. Administrator checks if webmail works but Outlook still fails

The Exchange administrator should check the following rather than reset the password repeatedly:

1. Autodiscover: For Exchange 2016, 2019, or Subscription Edition, confirm the Autodiscover SCP, external DNS record, certificate name, and externally reachable URL. Autodiscover supplies Outlook with the mailbox connection settings.^6^
2. External test: Run the Microsoft Remote Connectivity Analyzer, select the Autodiscover test, and then run the Outlook Connectivity test. A failed result should identify incorrect external URLs, DNS, certificate, or authentication configuration.^6^
3. Client compatibility: Confirm the Exchange version, Outlook build and installation source, and whether the published Exchange endpoints permit the authentication method required by that Outlook version.

Conditional: pure on-premises ADFS Modern Authentication

Apply this only if the organization has explicitly enabled pure on-premises ADFS Modern Authentication and meets all documented requirements: Outlook for Mac Microsoft 365 build 16.106 (26020821) or later, macOS Sequoia or later, and Exchange Server Subscription Edition with the December 2025 or later security update. Standalone Outlook 2024 for Mac is not supported for this scenario.^7^

Quit Outlook, then authorize the organization’s ADFS FQDN in Terminal. Do not include https:// or a trailing slash:

defaults write com.microsoft.Outlook \
  ADFSAuthorizedURLs -array fs.contoso.com

Replace fs.contoso.com with the administrator-provided ADFS FQDN. For multiple namespaces, put each hostname after -array, separated by spaces.

References

1. I can't connect to my Exchange account in Outlook for Mac | Microsoft Support
2. Add an email account to Outlook for Mac | Microsoft Support
3. Exchange account server settings | Microsoft Support
4. Add Exchange Server mailboxes in Outlook for Mac | Microsoft Support
5. Use Kerberos authentication with Outlook 2016 for Mac
6. Autodiscover service in Exchange Server
7. Enabling Modern Auth in Exchange on-premises